agar

agar

[ag´ahr]

a dried hydrophilic, colloidal substance extracted from various species of red algae. It is used in cultures for bacteria and other microorganisms, in making emulsions, and as a supporting medium in procedures such as immunodiffusion and electrophoresis. Because of its bulk it is also used in medicines to promote peristalsis and relieve constipation.

a·gar

(ah'gar, ā'gar),

A complex polysaccharide (a sulfated galactan) derived from seaweed (various red algae); used as a solidifying agent in culture media; it has the valuable properties of melting at 100°C, but not of solidifying until 49°C. Synthetic agars are also available.

[Bengalese]

agar

(ag´ahr) a dried hydrophilic, colloidal substance extracted from various species of red algae; used in solid culture media for bacteria and other microorganisms, as a bulk laxative, in making emulsions, and as a supporting medium in procedures such as immunodiffusion and electrophoresis.

agar

(ā′gär′, ä′gär′) also

agar-agar

(ā′gär-ā′gär′, ä′gär-ä′-)

n.

1. A gelatinous material derived from certain marine algae. It is used as a base for bacterial culture media and as a stabilizer and thickener in many food products.

2. A culture medium containing this material.

Agar

(1) AgarA gelatinous, sulfated polysaccharide extracted primarily from Gelidium cartilagineum, Gracilaria confervoides, and related species of red algae (seaweed); it melts at ±100ºC and solidifies at ±40ºC.Herbal medicine Agar has been used as a bulk laxative, as it is highly hydrophilic. Microbiology Agar is the most commonly used support medium for bacterial and fungal culture, as nutrients, antibiotics, salts and various growth enhancers and inhibitors are easily incorporated into the media.Agar is also used as an emulsifier in foods; it cannot be digested by humans.(2) AGARAustralian Group on Antimicrobial Resistance Study. An ongoing surveillance of antimicrobial resistance in Australian teaching hospitals,which began in 1986.

a·gar

(ā'gahr)

A complex polysaccharide (a sulfated galactan) derived from seaweed (various red algae); used as a solidifying agent in culture media. It has the valuable property of melting at 100°C but not solidifying above 49°C.

[Bengalese]

agar

A seaweed extract, sometimes called agar-agar, much used in bacteriological laboratories because it forms a convenient gel for the suspension of nutrient culture material, such as blood or broth, on which micro-organisms can be grown in an incubator.

agar

a complex POLYSACCHARIDE obtained from marine algae, which is widely used (in gel form) as a solidifying agent. Agar has two main components, agarose and agaropectin. Agar is used in various kinds of microbiological MEDIUM, and refined forms of agar or agarose are used in techniques such as ELECTROPHORESIS and gel filtration. In industry it is used as a gelling agent in foods such as jellies, soups and ice cream.

Agar has certain properties that make it particularly valuable in MICROBIOLOGY:

it is translucent or transparent and is degraded by only a few MICROORGANISMS.

it melts at about the boiling point of water, but remains liquid until the temperature has dropped to about 40–45 °C, when gelling occurs. Thus it can be poured over or mixed with a bacterial INOCULUM at about 50 °C, without injuring the bacteria. Once it has solidified it can be incubated at temperatures up to about 65 °C, perhaps higher, without liquifying. This is particularly useful where THERMOPHILIC microorganisms are being grown.

Agar medium is prepared by adding agar, often before autoclaving (see AUTOCLAVE), to the nutrients etc. of the medium. Agar medium is generally contained in a PETRI DISH (plate) or test tube. The test tubes containing agar are called ‘slants’ or ‘slopes’ when they allow the medium to set at an angle. When the agar solidifies in a vertical tube it is called a ‘deep’. In a Petri dish the medium solidifies as a layer over the base of the dish.

Agar

A gel made from red algae that is used to culture certain disease agents in the laboratory.

a·gar

(ā'gahr)

A complex polysaccharide (a sulfated galactan) derived from seaweed (various red algae); used as a solidifying agent in culture media.

[Bengalese]

agar

a dried hydrophilic, colloidal substance extracted from various species of red algae. When suspended in a liquid medium and heated to 212°F (100°C), the agar dissolves. When it is allowed to cool to 110°F (43°C) the medium becomes a solid gel. It is used in culture media for bacteria and other microorganisms, in making emulsions, and as a supporting medium for immunodiffusion and immunoelectrophoresis. Because of its bulk it is also used in medicines to promote peristalsis and relieve constipation.

birdseed agar

one containing Guizotia abyssinicia (Niger) seed and creatinine, used for growing Cryptococcus neoformans. Called also Niger agar.

bismuth sulfite agar

a special preparation used for isolation of salmonellae from food.

blood agar

a culture medium used for the growth of bacteria. Consists of agar and intact erythrocytes.

brain heart infusion agar

used for cultivating the yeast phase of dimorphic fungi.

brilliant green agar

used to cultivate salmonellae.

chocolate agar

an enriched agar for the growth of Hemophilus, some Actinobacillus, and Taylorella spp. A molten agar and blood mixture is held at 122°F (50°C) prior to pouring plates. The additional nutrients supplied are hemin and NAD.

23 The etiological diagnosis of UTI requires quantitative urine culture on standard agar media because only 20 to 30% of urine samples results in significant growth with predominant causative agents which are E.

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